(1) Field of the Invention
This invention relates to photosensitive films and similar articles useful in preparing visual aids, such as films for preparing montages, duplicating films, color guides, films for microfiches and similar microcopies, and generally wherever it is desired to have a mono- or polychromatic reproduction of an original (transparency or mask) useful in itself or as an intermediate. More particularly, this invention relates to negative-working photosensitive articles useful for making visual aids by imagewise exposure of a layer of a negative-working photosensitive photopolymerizable composition deposited on a transparent support to actinic light followed by development with water.
The articles of the present invention are generally useful in the field of planographic reproduction.
In our application filed on even date, mentioned above, we describe film-forming, oleophilic photopolymerizable compositions which are soluble in organic solvents. These compositions are suitable for use as the photosensitive layer of water-developable, negative-working lithographic plates when deposited as a layer (film) on a suitable hydrophilic support. These photopolymerizable compositions comprise at least one epoxy resin monomer or prepolymer which is fluid at ambient temperature and which has an epoxy equivalent of less than about 350, preferably less than about 200, and a photosensitive reaction product of a water-soluble, photosensitive condensation product of a diazonium compound and an organic condensation agent with an organic coupling agent which is capable of rendering the photosensitive reaction product soluble in organic solvent but only slightly soluble in water.
In the present invention, these same or similar photopolymerizable compositions, which may further include one or more dyes to obtain particular visual effects, are deposited on a transparent support, which is not hydrophilic, to obtain the photosensitive articles for making visual aids such as montages, duplicating films, color guides, microfiche films and the like.
(2) Discussion of the Prior Art
Planographic reproduction techniques are, of course, very old and have undergone extensive developments with respect to all of its different aspects, including the types of substrates, types of photosensitive compositions, types of inks, etc., as well as with respect to the development of new applications in the graphic arts.
As used in the present application, the term "visual aid" is intended to broadly include all types of image-bearing transparent films and plates, whether monochromatic or polychromatic images, clear or colored backgrounds, flexible or rigid supports, etc. Furthermore, the visual aids may be directly useful for displaying information (although appropriate projection or reading systems may be required, as with microfiche films) or they may simply be intended as screens or guides for preparing other products, such as montage films and color guide or selection films.
Montage films, for example, are used to provide a base film which can be used for registering and positioning the various colors of a montage. Generally, the montage films produce a faint blue color upon exposure. These films are not sensitive to ultraviolet light and therefore they can be used with color selection films without interfering with the copying of the latter.
Color guide (or color selection) films are films of the three complementary colors: cyan, magenta and yellow, which by superposition on a white background make it possible to see the final color that would be obtained, for example, by polychromatic lithographic printing. In addition, more than the three complementary colors can be used in these color guides when it is intended, for example, to use these films as transparencies in overhead projection units and the like.
"Graphic Arts" type duplicating films, such as those sold by du Pont de Nemours & Co. under their trademark CRONA-LITE are line and screen duplicating films having a rather high density. These films absorb ultraviolet light and are generally black in appearance.
Microfiche films are black-chestnut colored films which obviously require very dense but clear copy so that the microcopied information can be read on the microfiche readers with good contrast.
In all of these application, the support used is transparent and is preferably made of flexible plastic.
Color guide films are described in French Pat. No. 2,001,413, in particular in Example 17.
These films are developed, after exposure to ultraviolet rays through a screened original exhibiting transparent zones and opaque zones, with an aqueous solution containing 20% wetting agent such as sodium lauryl sulfate. To obtain a good development, without deterioration of the layer, it is, however, preferable to add a little acid to the developing solution.
The composition coated on the transparent polyester support is made up of a 5% solution, in methylcellosolve, of a condensation product of p-diazodiphenylamine with paraformaldehyde coupled with 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid and 2% of an epoxy resin EPON 1031 of the SHELL CHEMICAL COMPANY.
The visual aid articles, such as listed above, are generally handled without special precautions, and it is therefore necessary to use photosensitive layers having a good resistance to abrasion, i.e. having hardness and a good tenacity. For this purpose, photosensitive layers with an epoxy resin base are quite suitable.
However, the photosensitive layers as described above which are used in making visual aid articles have the drawback of requiring special developers.